全文获取类型
收费全文 | 85篇 |
免费 | 11篇 |
出版年
2023年 | 3篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 5篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 2篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1978年 | 1篇 |
1974年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1942年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有96条查询结果,搜索用时 15 毫秒
91.
92.
93.
Methanogenesis, fires and the regulation of atmospheric oxygen 总被引:2,自引:0,他引:2
The Gaia hypothesis states that the composition, oxidation-reduction potential and the temperature of the Earth's lower atmosphere are modulated by and for the biota living on the surface (Lovelock, 1972; Margulis and Lovelock, 1974). A corollary is that atmospheric oxygen is presently regulated at about 21% for the dominant life forms today: vascular plants and metazoa. We suggest that the enormous annual production of methane (of the order of 1014 mol) is directly related to the short term modulation of oxygen concentration. Atmospheric oxygen results from the burial of reduced carbon; methanogenesis and subsequent atmospheric oxidation of methane prevents that burial. We also present experimental work on the probability of ignition of vegetation as a function of increasing oxygen concentration (Watson, 1978). Both the experiments and consideration of the fossil record lead us to conclude that oxygen has been regulated by methane (and perhaps by N2O and others) at about 10–25% for very long periods relative to the atmospheric residence times of these reactive gases. 相似文献
94.
95.
The atmosphere of the earth differs greatly from that of the other terrestrial planets with respect to composition, acidity, redox potential and temperature history predicted from solar luminosity. From the fossil record it can be deduced that stable optimal conditions for the biosphere have prevailed for thousands of millions of years. We believe that these properties of the terrestrial atmosphere are best interpreted as evidence of homeostasis on a planetary scale maintained by life on the surface. Some possible mechanisms of this biological homeostasis have been noted and the implications of this concept for experimental studies pointed out. 相似文献
96.